High severity7.5NVD Advisory· Published Apr 10, 2026· Updated Apr 24, 2026
CVE-2026-34480
CVE-2026-34480
Description
Apache Log4j Core's XmlLayout https://logging.apache.org/log4j/2.x/manual/layouts.html#XmlLayout , in versions up to and including 2.25.3, fails to sanitize characters forbidden by the XML 1.0 specification https://www.w3.org/TR/xml/#charsets producing invalid XML output whenever a log message or MDC value contains such characters.
The impact depends on the StAX implementation in use:
- JRE built-in StAX: Forbidden characters are silently written to the output, producing malformed XML. Conforming parsers must reject such documents with a fatal error, which may cause downstream log-processing systems to drop the affected records.
- Alternative StAX implementations (e.g., Woodstox https://github.com/FasterXML/woodstox , a transitive dependency of the Jackson XML Dataformat module): An exception is thrown during the logging call, and the log event is never delivered to its intended appender, only to Log4j's internal status logger.
Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue by sanitizing forbidden characters before XML output.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
org.apache.logging.log4j:log4j-coreMaven | >= 2.0-alpha1, < 2.25.4 | 2.25.4 |
org.apache.logging.log4j:log4j-coreMaven | >= 3.0.0-alpha1, <= 3.0.0-beta3 | — |
Affected products
7cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*+ 6 more
- cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*range: >=2.0,<2.25.4
- cpe:2.3:a:apache:log4j:3.0.0:alpha1:*:*:*:*:*:*
- cpe:2.3:a:apache:log4j:3.0.0:alpha1_rc1:*:*:*:*:*:*
- cpe:2.3:a:apache:log4j:3.0.0:alpha1_rc2:*:*:*:*:*:*
- cpe:2.3:a:apache:log4j:3.0.0:beta1:*:*:*:*:*:*
- cpe:2.3:a:apache:log4j:3.0.0:beta2:*:*:*:*:*:*
- cpe:2.3:a:apache:log4j:3.0.0:beta3:*:*:*:*:*:*
Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
8- github.com/apache/logging-log4j2/pull/4077nvdIssue TrackingPatchWEB
- www.openwall.com/lists/oss-security/2026/04/10/9nvdMailing ListThird Party AdvisoryWEB
- github.com/advisories/GHSA-3pxv-7cmr-fjr4ghsaADVISORY
- lists.apache.org/thread/5x0hcnng0chhghp6jgjdp3qmbbhfjzhbnvdMailing ListVendor AdvisoryWEB
- logging.apache.org/security.htmlnvdVendor AdvisoryWEB
- nvd.nist.gov/vuln/detail/CVE-2026-34480ghsaADVISORY
- logging.apache.org/cyclonedx/vdr.xmlnvdProductWEB
- logging.apache.org/log4j/2.x/manual/layouts.htmlnvdTechnical DescriptionWEB
News mentions
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